The present invention relates, in general, to watthour meters and/or watthour meters socket adapters.
Electrical power is supplied by an electric utility to individual use sites by power line conductors which extend from the utility poles to a meter socket mounted on a convenient surface at the use site. The power line conductors are physically connected to line jaw contacts in the meter socket. Distribution conductors extend from load jaws mounted in the socket throughout the use site.
An electric power watthour meter is provided for measuring the power consumed by a use site by measuring the current drawn by the use site from the line to the load conductors. A watthour meter typically has a base on which metering components are mounted. Blade terminals extend from the base for interconnection in the socket line and load jaw contacts so as to place the meter in series between the power line conductors and the power load conductors. A dome historically formed of glass surrounds the electro-mechanical metering components mounted on the watthour meter base. The dome includes a mounting flange which overlays a flange on the base and is fixed to the base by a metal mounting ring. A seal is used to then secure the dome to the base.
With the advent of electronic meters and automatic meter reading equipment, the glass dome has been replaced with a plastic dome or cover typically having a view window in an end wall for viewing an electronic display of power consumption. The mounting flange on the plastic domes are formed with slots for engagement with a standard meter base carrying the blade terminals and metering components.
The watthour meter is installed in the socket and/or in a socket adapter or socket extender which is mounted in the socket which also carries mating jaw contacts by inserting the meter blade terminals into the meter socket or socket adapter jaw contacts.
A concern which arises with any watthour meter design, whether of the automatic reading type or a more conventional, electronic or mechanical watthour meter, is the ability to detect tampering with the meter, such as the removal of the meter to insert wires to bypass the meter and thereby obtain free, unmetered power. In addition to removing the meter, certain tampering events involve the removal and the replacement of the meter in an inverted position in the socket so as to cause reversal of the rotation of the measuring disk.
Other tampering efforts have involved separation of the meter dome from the meter base to enable tampering with the internal mechanical, electronic, or electrical components of the meter in order to obtain free power.
On-site inspections of watthour meter mounting configuration by utility personnel have become less frequent. This has encouraged would be tamperers to increase their efforts to unauthorizedly obtain electric power from the meter socket without payment. This is despite the elaborate anti-tampering design features built into each watthour meter, meter socket adapter and meter socket and other tampering detection circuits and devices.
Older tamper detection devices were mechanical in nature and frequently included an orientation sensitive switch, also known as a tilt switch, which detected reverse mounting of the watthour meter in the socket after the meter is first removed from the socket. Once removed, a single phase meter could be installed upside down resulting in reverse rotation of the meter disc and register dials which record cumulative energy consumption. The existence of a single tampering event or the recording of the number of times a tampering event was typically detected and stored in a memory device in the watthour meter.
While effective, such mechanical tampering detection devices still require some type of on-site inspection to determine the tamper detection elements detected a tampering event.
One method of providing a tamper indication between the meter dome or cover and the meter base is shown in FIG. 1 and involves the use of a metal T-shaped seal. The seal, which typically is formed of aluminum, has a generally flat head and an elongated, bendable stem. The stem is inserted through aligned apertures in the metal band surrounding the meter dome flange and the base flange.
During assembly of the watthour meter, after the dome is mounted on the base, the T-seal is inserted stem first through aligned apertures in the ring and base. As the end of the stem passes through an aperture in the base it encounters a ramp surface which bends the end of the stem out of the plane of the remainder of the stem. The end is further bent back manually over the stem itself as shown in FIG. 1 to lock the seal on the base.
In use, any attempt to pull the T-seal from the base, will cause the bent end to sever from the remainder of the stem thereby providing an indication of a tamper event.
However, since the meter is normally mounted in a socket when tampering occurs, the separation of the end of the stem from the T-seal causes the short metal end to fall into the interior of the socket which is carrying voltage. This metal piece could create a dangerous arcing condition.
Thus, it would be desirable to provide a safer means for sealing or providing a tamper indication lock of a meter dome and/or a cover to a meter base which avoids problems associated with prior art meter seals.
It would also be desirable to provide a watthour meter having an approved tamper event detection which effectively detects any initial separation of a watthour meter from the meter socket jaws which is capable of providing a tamper detection event signal which can be transmitted internally and/or externally of the watthour meter.